The invention relates to techniques for electronically varying the partitioning of planar arrays or phase scanned arrays into sub-arrays, and in particular to an improved technique for providing electronic roll stabilization of the array difference patterns.
The method generally used to generate sum and difference patterns in gimballed planar arrays or phased scanned arrays is to partition the array into quadrants with a separate output for each. The appropriate quadrant outputs are summed or differenced to provide a sum pattern and two difference patterns. The two difference patterns provide tracking error signals referenced to the antenna.
In many airborne radar modes, in particular the terrain following and terrain avoidance modes, difference patterns stabilized with respect to the horizon are required. The current solution to this problem is either to provide a third gimbal or to implement rather cumbersome and not entirely satisfactory signal processing to derive roll stabilized tracking outputs. The roll gimbal technique is probably not feasible for active array systems of sufficient size to require liquid cooling. An alternative to the signal processing approach is needed.
It would therefore represent an advance in the art to provide an electronically roll stabilized active array without the need for mechanical roll gimbals or cumbersome signal processing.